Grass cutting machine

ABSTRACT

A grass cutting machine has two forward cutting units (24) and one rear central unit (46). The mechanism at, for example, the margin of a golf green, provides a time delay between lifting or lowering of the front (24) and rear cutting units (46) which is determined by the distance travelled by the machine. In this way it is ensured that all unites start and stop cutting at the same reference point on the ground.

This invention relates to grass cutting machines with particularemphasis on machines for cutting golf greens.

When cutting golf greens, it is desirable for the cutting unit to beraised and lowered with precision at the margins of the green. With asingle cutting unit, this can be simply achieved by the manual operationof a lifting handle. Where the machine carries more than one unit (andthere are usually three cutting units) it is necessary for a mechanicallifting mechanism to be provided. As will be well understood, threecutting units cannot be positioned in a single transverse line since thetotal width of each unit exceeds the cutting width. A transverse in-linearrangement would therefore leave strips of grass uncut. To overcomethis problem, three cutting units are typically arranged as a pair ofwing cutters and a single central cutter positioned either in front ofor behind the wing cutters.

If the spacing of the wing and central cutting units in the direction ofmotion is kept to a minimum, all three cutting units can be lowered orlifted simultaneously without significant degradation of the boundarybetween cut and uncut grass at the green edge. There are, however,problems in having all three cutting units so close together and forthis reason prior art designs have often incorporated a significantspacing between the units in the direction of motion. Simultaneouslowering or lifting of all units would then tend to degrade the cutgreen boundary since the points on the ground at which the front andrear cutting units started or stopped cutting would be a significantdistance apart. It has been proposed to introduce a time delay betweenthe lowering of the front and rear units and between the lifting of thefront and rear cutting units. This has not however, satisfactorilyresolved the problem.

It is an object of this invention to provide an improved grass cuttingmachine in which cutting operations of cutting units spaced in thedirection of motion of a moving machine are started at substantially thesame reference point on the ground and, similarly, halted atsubstantially the same reference point. It will be understood thatcutting operations of a unit can be started by lowering the unit to theground or by engaging drive to an already lowered unit. Similarly,cutting operations can be halted by lifting a unit or by disengagingdrive to the unit.

The present invention consists, in one aspect, in a grass cuttingmachine having spaced forward and rearward cutting units; respectiveunit control means for starting and stopping cutting operations of theunits and common control means adapted to actuate said unit controlmeans in response to a common cutting start signal or a common cuttingstop signal, wherein there are provided distance transducer meansadapted to supply the common control means with a distance signalindicative of the distance travelled by the machine, the common controlmeans being adapted to space actuation of the respective unit controlmeans by a time interval computed in response to said distance signaland the known separation of the cutting units in the direction of motionsuch that, when the machine is moving, the cutting units start cuttingoperations at substantially the same point on the ground and stopcutting operations at substantially the same point on the ground.Preferably, there are further provided speed threshold means adapted tosupply the common control means with a speed signal indicative ofwhether the ground speed of the machine is above or below a pre-setthreshold; the common control means being switched between a servicemode corresponding to zero or very low ground speeds and a cutting modecorresponding to significant ground speeds in dependence on said speedsignal and adapted in said service mode, to actuate said unit controlmeans simultaneously in response to a common cutting start signal or acommon cutting stop signal and, in said cutting mode, to space actuationof the respective unit control means by said time interval.

It will be understood that since the time delay between stopping orstarting cutting operations of the forward and rearward cutting units iscomputed from the distance travelled by the machine, the boundarybetween cut and uncut grass remains well defined even if the groundspeed of the machine varies. The preferred form of the invention inwhich the common control means is switched between a service mode and acutting mode in dependence upon the value of the speed signal, enables avery simple distance transducer to be used with correspondingly simplecontrol circuitry. The skilled man will appreciate that a simpledistance transducer will have difficulty in distinguishing between zeroand very low forward speed. By ensuring that the delay is onlyintroduced at ground speeds above a predetermined minimum, such problemsare avoided.

It is an object of a further aspect of this invention to provide animproved grass cutting machine in which the operator is provided withaccurate information relating to the quality of cut. Conventionally, thequality of cut of a grass cutting machine is defined in terms of either"cuts per meter" which is the number of reel blade passes for one meterof forward movement of the machine, or "inch-clip" which is the distancein inches along the ground between successive blade passes. If theground speed and cutting reel speed vary independently, there is adanger that the operator will depart inadvertently from a desiredquality of cut standard. In the past, a graph has been supplied witheach machine from which the operator can determine the quality of cutfrom his knowledge of both reel speed and ground speed. Whilst thisprovides the necessary information, it is a cumbersome and timeconsuming procedure for the operator. Another proposal has been to markthe scale of movement of the ground speed control lever with "coarse"and "fine" bands indicating whether the quality of cut (at an assumedreel speed) is above or blow a predetermined threshold. Whilst thisapproach has the merit of simplicity, it is believed that more accuratequality of cut information would be beneficial.

Accordingly, the present invention consists, in a further aspect, in agrass cutting machine having at least one cutting reel unit; groundspeed sensor means for providing an electrical signal indicative of theground speed of the machine; reel speed sensor means for providing anelectrical signal indicative of the driven reel speed of the cuttingunit; processor means for computing from said signals a value for thequality of the cut; and display means for displaying said quality of cutvalue.

This invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is a plan view, in partly schematic form, of a grass cuttingmachine according to this invention;

FIG. 2 is a side view of the machine showing the mounting of the grasscutting units;

FIG. 3 is hydraulic circuit diagram of the machine shown in FIG. 1;

FIG. 4 is an electrical circuit diagram of the machine shown in FIG. 1;

FIGS. 5A and 5B are diagrams illustrating details of the circuit of FIG.4;

FIG. 6 is a circuit diagram illustrating in further detail of thecircuit of FIG. 4;

FIGS. 7A and 7B are sketches illustrating the quality of cutcomputation;

FIG. 8 is a series of waveforms illustrating the operation the circuitof FIG. 4; and

FIG. 9 is a truth table illustrating the operation of the hydrauliccircuit of FIG. 3.

The grass cutting machine shown in the drawings at 10 comprises anA-frame chassis 12 supported on two front wheels 14 and a rear wheel 16.The chassis carries, towards the rear, a conventional diesel engine 18which provides the traction drive for the machine through the frontwheels 14, via a hydrostatic transmission (not shown). The engine 18also power a hydraulic pump 20 which, as will be described, provides adrive for the cutting units as well as the powered lifting mechanism forthose cutting units. The rear wheel 16 is steerable through a steeringwheel 22 which is position adjacent the operator's seat 23. Suitablebodywork 21 is mounted on the chassis.

So far as described above, the grass cutting machine is of generallyconventional form and more detailed description of the mentionedcomponents is not believed to be necessary for an understanding of thepresent invention.

Two forward cutting units 24 of the reel type are supported from thechassis on respective support arms 26 each pivotally mounted withrespect to the chassis on an axle 28. Each cutting unit is provided witha hydraulic drive motor 30 receiving hydraulic fluid through lines 32.Each cutting unit further includes a grass box 34. To enable lifting ofeach cutting unit from the cutting position shown in the drawings, alift arm 36 pivotally mounted on the chassis at 38 is connected at itsfree end to the cutting unit by a cable 40. A crank plate 42 is formedintegrally with the lift arm adjacent the axis 38 and a hydrauliclifting ram 44 extends between the crank plate and a rearward locationin the chassis. It will be recognised that upon extension of thehydraulic ram 44, the lift arm 36 is caused to pivot anti-clockwise (asseen in FIG. 2) so lifting the cutting unit with pivotal movement of thesupport arm 26 about axle 28.

A rearward central cutting unit 46 driven through hydraulic motor 47 ispositioned beneath and slightly to the rear of the operator's seat 23.In a analogous with the front cutting units, the unit 46 is supportedfrom a pivotally mounted support arm 48. A lift arm 50 pivotally mountedon the chassis at 52 is connected at its free end to the cutting unit 46by a cable 54. A hydraulic lifting ram 56 extends between the chassisand the mid-length of the lift arm 50 to enable lifting of the cuttingunit by anticlockwise rotation (as seen in FIG. 2) of the lift arm aboutaxis 52.

The operator controls on the machine include a foot pedal 58 controllingforward and rearward movement of the machine and a foot pedal 60controlling the lifting and the lowering of the units, this latter footpedal being linked with a hand lever (not shown) which effectively locksthe units in the lifted position. In addition, the controls include apush button console 62.

The hydraulic circuit of the machine is shown in FIG. 3. The hydraulicpump 20 is adapted to be continuously driven and is connected with thetank 64 by a solenoid operated valve SK. This valve is normally open sothat hydraulic fluid is recycled to the tank. Valve SK is connectedthrough a reel reversing valve 65 with the serially interconnectedcutting unit hydraulic motors 47, 30L (left) 30R (right). Each cuttingmotor is provided with a by-pass loop 66 controlled by a by-pass valve68. These by-pass valves are mechanically linked in a manner not shownin the drawings with the lifting arms associated with the respectivecutting units such that when the cutting unit is in the lifted position,the by-pass valve 68 effectively disables the motor. In parallel withcutting motor 47 (driving rearward cutting unit 46) there is mounted asolenoid operated valve SM. Similarly, a solenoid operated vlave SL isconnected in parallel with cutting motors M2 and M3. In this way,independent control may be exercised over the rearward cutting unit 46or, the forward cutting units 24.

Fluid which has either passed through or by-passed the cutting motorsreturns via the reel reversing valve 65. Connection is made from thisvalve to a parallel arrangement of three solenoid operated valves, ST,SS, and SR associated respectively with the lifting rams 56, 44L and44R. In the case of lifting rams 44 L and R the connection is madedirectly from the reversing valve 65; in the case of lifting ram 56 theconnection is through a solenoid operated valve SV. This valve isadditionally connected with a further solenoid operated valve SUoffering a return path to the tank.

A check valve 70 is interposed between the reel reversing valve 65 andthe solenoid valves SR, SS and SV. Upstream of this check valve 70 thereis provided an alternative return path to the tank through pressurerelief valve 72.

It is considered preferable to describe the manner of operation of thehydraulic circuit before dealing in detail with the electronic circuitrywhich serves to operate the solenoid valves.

If it is assumed that the machine is approaching a golf green atreasonable speed with all three lift rams in the up position, theoperator will actuate the foot pedal 60 to lower the front cutting unitsat the correct point. Valve SK is opened so providing pressurised fluidto the circuit and at the same time valves SU and ST are actuated. Sincelifting rams 44 now have a return path to tank through valves SV and SU,the associated forward cutting units 24 fall under gravity. Theactuation of valve ST to the closed state maintains lifting ram 56 inthe up position. With valves SL and SM normally closed, the cuttingmotors will be under control of the associated by-pass valves, that isto say cutting motors 30 will be energised as the forward lift arms fallwhilst cutting motor 47 will remain disabled.

After a delay which is derived in a manner to be described, solenoidvalve ST is released to return to the normally open position thusallowing fluid to flow from the ram 56 through the valve SU to the tank,the rearward cutting unit 46 therefore falls and begins to rotate as theby-pass vaklve is opened.

If the control pedal is released because, for example, the machine isleaving the green, valve SL is actuated to by-pass cutting motors 30 andthus halt cutting operations of forward cutting units 24. After thementioned delay, valve SK is operated so effectively disabling all threecutting motors. If the operator then moves the foot pedal to the liftposition solenoid valve SK is closed with the result that, with valve SUremaining closed, all three lifting rams are supplied with hydraulicfluid to lift pressure determined by relief valve 72. Since valve SK isbeing closed, it is necessary to open both valves SL and SM to ensurethat all cutting motors remain stationary.

Referring now to FIG. 4, there is shown in outline the electricalcircuitry which provides the necessary signals to actuate the solenoidvalves K, L, M, R, S, T, U and V. It will be seen that a logic unit 74receives inputs from the console 62, the foot pedal 60 and a microswitch 76 indicating whether the reels are being driven forward in anormal cutting operation or backward for backlapping. The logic unitalso receives signals from a speed detecting unit 78 and a space delayunit 80 which will be described more fully hereafter. The principaloutputs of the logic unit comprises a series of logic outputs one eachfor the solenoid valves. These are converted in a solenoid drive unit 82to signals of a sufficient power to actuate the solenoid valves.

The speed detecting units 78 and space delay unit 80 receive in parallelan output from a wheel transducer 83. As shown diagrammatically, one ofthe wheels of the machine is provided with a coaxial disc 84 having anumber of equally spaced holes 86 around the perimeter. An opticalswitch 88 comprising a collimated infra-red light source on one side ofthe disc and a phototransistor on the other serves to provide a streamof pulses whose repetition rate is proportional to the disc speed andthus to the ground speed of the machine.

Referring now to FIG. 5B, the space delay unit 80 will be described inmore detail. The output of the wheel transducer 83 is supplied to NORgate G1. If the foot pedal 60 is moved from neutral to down or releasedfrom down to neutral a signal will appear as will be described on eitherof the inputs to NOR gate G2 thus setting the flip-flop constituted byNOR gates G3 and G4. This has the two effects of setting the SPACE DELAYline high and also allowing pulses from the wheel transducer through tothe counter C1. Counter C1 produced an output pulse after counting 16input pulses which resets the flip-flop and returns the SPACE DELAY lineto the low level. Turning now to FIG. 5A, the wheel transducer output ispresented to a monostable MA providing inverted and non-inverted outputsQA and QA respectively. QA is connected with a further monostable MB,the output of which is OR'd by diode gate G5 with QA. If the period ofwheel pulses is less than the output pulse length of monostable MA, thatis to say if the wheel speed is above a predetermined minimum, QA willbe continuously retriggered and will remain high. Signal QA will remaincontinuously low and since the input to monostable MB is not pulsed theoutput QB will remain similarly low. It follows that the line HIGH IFSPEED LOW will remain low. If the wheel speed drops below thepredetermined minimum, the period of the wheel-pulses will exceed thepulse length of monostable MA so that outputs QA and QA become pulsed.An output QB is now produced from monostable MB and it will be seen fromthe timing diagram which is FIG. 8 that the effect of OR'ing QB and QAis to produce a continuously high signal on line HIGH IF SPEED LOW

The logic unit 74 is shown in FIG. 6. It will be seen that the PEDALDOWN and PEDAL UP signals from foot pedal 60 are each AND'ed with theHIGH IF SPEED LOW line in gates G6 and G7 respectively. The effect isthat foot pedal control is disabled in a service mode at low speed. Inaddition, the output from AND gate G6 is connected directly to acapacitor C1 and--via NOR gate G8--to a capacitor C2. The respectiveopposite terminals of capacitors C1 and C2 form the previously mentionedinputs to NOR gate G2 shown in FIG. 5A, the capacitors C1 and C2,together with the grounded resistors R1 and R2 forming a differentiatingnetwork which provides pulses at the positive and negative going edgesof the PEDAL DOWN signal.

The outputs from AND gates G6 and G7 form the set and reset inputs of aflip-flop F1. The output lines PEDAL DOWN (PD) from gate G6, PEDAL UP(PU) from gate G7, FF from flip-flop F1 and PD from NOR gate G8 areconnected as will be described with the logic circuitry driving theouput lines of the logic unit. These output lines correspondrespectively with the solenoid valves K, L, M, R, S, T, U and V.

Line PD is connected as one input to a diode OR gate D1 the output ofwhich is connected with output line K. The line PD is further connectedas an input to AND gate G9 connected in turn to diode OR gate D4 drivingoutput line T. Line PU forms a further input to diode OR gate D1 and isconnected also as an input to diode OR gate D2 driving ouput line L.Further connections are made between line PU and AND gate G10 forming aninput to diode OR gate D3 driving output line M, and to AND gate G11connected to diode OR gate D6 driving output line U. Line FF forms afurther input to diode OR gate D6 and line PD is connected to AND gateG12 the output of which is taken to diode OR gate D2.

One set of outputs from the operator console 62 are designated as linesLOWER, RUN, LIFT and OFF. The LOWER, RUN and LIFT lines are associatedrespectively with flip-flops respectively F2, F3 and F4. The LOWER andRUN lines are connected respectively with the set inputs of flip-flopsF2 and F3; the LIFT line is connected with the set input of flip-flop F4through a delay unit 90. Each of the flip-flops F2, F3 and F4 has areset line connected with a diode resetting matrix 92. This matrixreceives as inputs, the OFF line and the HIGH IF SPEED LOW LINE andserves to disable all three flip-flops if the HIGH IF SPEED LOW line islow (indicating that the machine is in the cutting mode) or if the OFFbutton is energised. In addition, the diode resetting matrix receives asan input the set input of each flip-flop so that setting any one of thethree flip-flops F2, F3 and F4 automatically resets the other two.Selection of the LOWER, RUN and LIFT console buttons is thereforemutually exclusive. A further set of operator console comprise HOLDlines HO1, HO2 and HO3, corresponding respectively with the cuttingunits and a reverse output REV which is energised when the wheels are tobe driven in reverse for backlapping. These console outputs areconnected with the above described logic circuitry as follows. Theoutput of flip-flop F2 (LWR) forms an input to diode OR gate D6. Theoutput of flip-flop F3 (RUN) forms inputs to diode OR gates D1 and D6and is also connected to AND gate G13 forming an input to diode OR gateD2. The output of flip-flop F4 (LIFT) forms inputs to diode OR gates D1,D2 and D3. HOLD line HO1 forms the second input to diode OR gate D4whereas HOLD lines HO2 and HO3 are directly connected to output lines Sand T respectively. Line REV is connected as the second input to ANDgate G13. To complete the logic circuitry the SPACE DELAY line isconnected to OR gate D1, AND gates G9 and G11 and G2 and to NOR gate G14forming the second input to AND gate G10.

It will be understood that two distinct modes of operation are defined;a service mode which applies when the machine is stationary ortravelling at a very low speed and a cutting mode. Switching betweenthese two modes is effected by the HIGH IF SPEED LOW line. In thecutting mode, the foot pedal 60 is enabled. To take one example, itwould be seen that depression of the foot pedal giving a signal on linePD serves through OR gate D1 to energise valve K. The set output FFsimilarly energises valve SU through OR gate D6. Solenoid valve ST isinitially energised through the AND'ing of signals PD and SPACE DELAY ingate G9 through OR gate D4. As the SPACE DELAY signal returns to low,solenoid valve ST is de-energised as required in the above describedsequence of operation of the hydraulic circuit.

In the service mode, when the line HIGH IF SPEED LOW is high, the footpedal is disabled. If the operator console LOWER button is energised,solenoid valve SU is energised through line LWR and OR gate D6 allowingall three cutting units to fall under gravity simultaneously. Similarly,the three cutting units ca be lifted simultaneously by the closing ofvalve SK through OR gate D1 and line LIFT. To avoid the dangers thatwould be associated with continuous energisation of the lifting rams,the delay unit 90 is provided so that flip-flop F4 is resetautomatically after a selected delay typically in the range of 5 to 10seconds.

In order to clarify further the operation of the logic unit, referenceshould be made to FIG. 9 which takes the form of a truth table. In thecutting mode, where the console buttons are disabled, the operator hasthe choice of two foot pedal sequences. Either, the foot pedal can firstbe moved to the neutral position to stop the cutting units with theappropriate delay and then moved to the LIFT position to lift all threeunits simultanously, or, in a single operation the pedal can be moved tothe LIFT position to lift the front cutting units and, after anappropriate delay, the rear cutting unit. In this sequence, the cuttingunits are stopped automatically when they reach their lifted position aspreviously described.

The output from the wheel transducer 83 is additionally used, asillustrated in FIG. 7A to produce a quality of cut display on theconsole. A similar apertured disc--and optical switch arrangement--tothat forming the wheel transducer is provided on a drive pulley of thepump, the rotation of which pulley is chosed to be proportional to reelspeed. In the case in which it is desired to produce a display of cutsper meter, the output from the wheel transducer is divided by 16 in afrequency divider. The output of the divider is AND'ed with thetransducer on the pump output. The output of the AND gate is fed to acounter which drives the cuts per meter display. It will be understoodthat the divider effectively defines a time window corresponding to adistance travelled by the machine and the counter effectively counts thenumber of blade passes within that distance.

It is a simple matter to produce optionally an "inch-clip" measurementin which case, as shown in FIG. 7B, the ouput from the pump transducerdefines the time window in which pulses from the wheel transducer arecounted. Preferably, both circuits are provided and the option selectedby a simple switch.

We claim:
 1. A grass cutting machine comprising:(a) spaced forward andrearward cutting units; (b) respective unit control means connected toreceive actuating signals and adapted in response to said actuatingsignals for starting and stopping cutting operations of the cuttingunits; (c) distance transducer means for providing a distance signalindicative of the distance of travel of the machine; (d) operatoractuable means for providing a common cutting start signal and a commoncutting stop signal; and (e) common control means connected to receivesaid distance signal, said common cutting start signal and said commoncutting stop signal and adapted on receipt of said common cutting startsignal or said common cutting stop signal to provide actuating signalsto said respective unit controls means, said actuating signals beingspaced by a time interval computed by the common control means inresponse to said distance signal and the known separation of the cuttingunits in the direction of motion of the machine such that, irrespectiveof the speed of travel of the machine, the forward and rearward cuttingunits start cutting operations at substantially the same point on theground and stop cutting operations at substantially the same point onthe ground.
 2. A grass machine according to claim 1, wherein there arefurther provided speed threshold means adapted to supply the commoncontrol means with a speed signal indicative of whether the ground speedof the machine is above or below a pre-set threshold; the common controlmeans being switched between a service mode corresponding to zero orvery low ground speeds and a cutting mode corresponding to significantground speeds in dependence on said speed signal and adapted in saidservice mode, to actuate said unit control means simultaneously inresponse to a common cutting start signal or a common cutting stopsignal and, in said cutting mode, to space actuation of the respectiveunit control means by said time interval.
 3. A grass cutting machinehaving at least one cutting reel unit; ground speed sensor means forproviding an electrical signal indicative of the ground speed of themachine; reel speed sensor means for providing an electrical signalindicative of the driven reel speed of the cutting unit; processor meansfor computing from said signals a value for the quality of the cut; anddisplay means for displaying said quality of cut value.